Quantifying entropy production in active fluctuations of the hair-cell bundle from time irreversibility and uncertainty relations

TL;DR

This paper develops methods to estimate entropy production in active biological systems by analyzing time irreversibility, applying them to hair-cell oscillations, and providing bounds that relate to thermodynamic efficiency.

Contribution

It introduces new irreversibility measures for active fluctuations and demonstrates their application to biological hair-bundle oscillations, estimating entropy production rates.

Findings

Irreversibility measures reveal active oscillations in hair-bundles.

Estimated entropy production rate is at least ~3 k_B/s.

Measuring additional transduction current tightens entropy bounds up to ~10^3 k_B/s.

Abstract

We introduce lower bounds for the rate of entropy production of an active stochastic process by quantifying the irreversibility of stochastic traces obtained from mesoscopic degrees of freedom. Our measures of irreversibility reveal signatures of time's arrow and provide bounds for entropy production even in the case of active fluctuations that have no drift. We apply these irreversibility measures to experimental recordings of spontaneous hair-bundle oscillations in mechanosensory hair cells from the ear of the bullfrog. By analysing the fluctuations of only the tip position of hair bundles, we reveal irreversibility in active oscillations and estimate an associated rate of entropy production of at least $\sim 3 k_{\rm B}$/s, on average. Applying thermodynamic uncertainty relations, we predict that measuring both the tip position of the hair bundle and the mechano-electrical transduction current that enters the hair cell leads to tighter lower bounds for the rate of entropy production, up to $\sim 10^3 k_{\rm B}$/s in the oscillatory regime.